A navigation system performs travel guidance for enabling a user to easily and quickly reach the selected destination. A typical example is a vehicle navigation system where a vehicle equips with a navigation function to guide a driver to a destination. Such a navigation system detects the position of the user or user's vehicle, reads out map data pertaining to an area at the current vehicle position from a data storage medium. Alternatively, such map data can be provided to the user from a remote server through a communication network such as Internet.
When a destination is set, the navigation system starts a route guidance function for guiding a user along a calculated route from the start point to the destination. During the route guidance, the navigation system reads the nodes data from the data storage medium such as DVD and successively stores the nodes data of road segments constituting the guided route in a memory. In the actual traveling, the node series stored in the memory is searched for a portion of the guided route to be displayed in a map display area of the monitor screen, and the portion of the guided route is highlighted so as to be clearly discernible from other routes. When the vehicle is within a predetermined distance from an intersection it is approaching, a highlighted intersection diagram with an arrow indicating the direction to turn at the intersection is displayed to inform the user of the appropriate road and direction at the intersection.
FIGS. 1A-1H show an example of overall procedure and screen display involved in the navigation system. FIG. 1A shows an example of locator map screen of the navigation system when the destination is not specified. Typically, the navigation system displays a street on which the vehicle (current vehicle position VP) is running on a map image and a name of the street. When selecting a “Destination” menu on a main menu screen (not shown), the navigation system displays an “Find Destination By” screen as shown in FIG. 1B for specifying an input method for selecting the destination.
The “Find Destination By” screen of FIG. 1B lists various methods for selecting the destination. The list includes a “Point of Interest (POI)” method for selecting the programmed destination based on the name, category or telephone number. When selecting, for example, the “Point of Interest (POI)” method, the navigation system displays selection methods of point of interest (POI) either by “Place Name” or “Place Type” in FIG. 1C. The “Place Name” is to specify a name of POI, and the “Place Type” is to specify a category or type of POIs. Suppose the “Place Type” is selected, the navigation system shows an “Select Category” screen such as shown in FIG. 1D.
Suppose the user selects “Restaurant”, the navigation system retrieves the POIs in the selected category, restaurant, as shown in FIG. 1E. Typically, names of POIs (restaurants) will be listed in the order of distance from the user (ex. current vehicle position). If the user selects a particular restaurant from the list, the navigation system displays a “Confirm Route” screen such as shown in FIG. 1F. In this example, the “Confirm Route” screen lists the name, address and phone number of the destination (POI specified by the user). If this is the correct destination, the user enters an “OK to Proceed” key to proceed to the next procedure.
In FIG. 1G, the navigation system calculates and determines a route to the destination, i.e., the selected POI. The navigation system determines a route to the destination based on predetermined rules such as a shortest way to reach the destination. Then, the navigation system starts the route guidance as shown in FIG. 1H to guide the user along the calculated route to the destination. Typically, the navigation system shows the intersection which is highlighted to show the next turn and a direction of the turn. Such route guidance by the navigation system is also accompanied by voice instructions.
The navigation system continues route guidance to the selected destination until the user reaches the destination or the user manually disables the guidance. The navigation system has a map data which is mainly comprised of nodes and links. The nodes are coordinate points that specify, for example, intersections, ends of roads, turning points, and border points between meshes. The links are connections between the nodes.
FIGS. 2A-2D are schematic diagrams showing the process involved in detecting an arrival at a destination where the destination is a large facility such as a shopping mall or a natural monument such as a lake or park, etc. In FIG. 2A, a vehicle 15 is heading to a POI 20 (destination) by following the route guidance provided by the navigation system. As shown in FIGS. 2A-2D, the actual POI 20 is a relatively large facility or natural monument as it occupies a large area. Based on the map data, a POI is assigned with an address point at one location of the POI. In the case of FIGS. 2A-2D, the navigation system has address data indicating a particular address 21 of the POI 20.
As the vehicle approaches the POI 20, the navigation system starts to operate arrival detection. FIG. 2B shows a schematic diagram showing a conceptual view of how to determine the arrival at the POI 20. As the vehicle 15 approaches the address point 21, the navigation system will start the arrival search by constantly checking if the address point 21 is within a predetermined arrival detection range 18. The arrival detection range 18 is, for example, a circle of 200-300 feet radius.
Thus, the navigation system measures a distance between the vehicle 15 and the address point 21 of the POI 20 to check whether the address point 21 of the POI 20 is within the arrival detection range 18. When the vehicle 15 reaches a point where the address point 21 comes within the arrival detection range 18, such as 200 feet, as shown in FIG. 2C, the navigation system determines the arrival and announces that the user has arrived at the destination. If there is an entrance 24 near the address 21, the user will make a turn and enter the POI 20 through the entrance 24.
In the conventional technology, a problem arises when the destination is a large POI occupying a large area as in FIGS. 2A-2D. Despite its large space, the navigation system recognizes a location of a large POI as a point, namely, a particular address of the POI. Thus, the navigation system will not determine that the vehicle 15 has reached the POI 20 unless the vehicle 15 comes close to the address point 21 so that the point of the address 21 comes within the arrival detection range 18.
There is a case when the user does not want to go that far to the particular address point of the POI 20 to satisfy the objective. For example, in the case where the POI 20 is a stadium, the POI 20 has several entrances 23-25 as shown in FIGS. 2B-2D. Suppose the user has a ticket for the stadium where the seat for the user is located close to the entrance 23 of the POI 20 (stadium). In the conventional technology, the navigation system guides the user to the particular address point 21 of the stadium.
Therefore, in such a situation, it is preferable that the navigation system announces the arrival of the destination earlier so that the user drives the vehicle 15 to the entrance 23 of the stadium as shown in FIG. 2D. However, the navigation system will fail to recognize that the vehicle has arrived in FIG. 2D. This is because the address point 21 has not come within the arrival detection range 18. Thus, despite the actual arrival, the navigation system keeps guiding the user to the address point of the destination. The user will have to cancel the operation to stop the route guidance, which would interfere with safe driving. Accordingly, there is a need of a new method and system to more effectively detect arrival at a destination which is a large scale POI.